The present invention relates to a drum-roller machine, and more particularly to a double transport drum-roller machine.
The tightness with which a web-formed material is rolled is important for and in maintaining the quality of the material when rolled on the roller, as well as the stability of the roller itself. In regulating the tightness with which the material is rolled, it is known in the art how to feed the web-formed material to the roller under tension, how to drive the two transport drums on a differential basis, and how to decrease the surface pressure of the roller on the drum by removing weight from the roller, which weight increases quadratically with increasing roller diameter.
In known double transport drum-roller machines, a mechanism engages both ends of the roller for relieving weight therefrom. For this purpose, the web-formed material is rolled onto a roller shaft having terminal segments projecting from both ends thereof so that counterforces may be applied thereto to counteract the weight force of the roller. The weight relieved in such a manner from the roller is also relieved from both transport drums. However, the weight relief provided will be diminished or fail if the axial length of the roller is quite large. This may be temporarily overcome by utilizing a roller shaft having physical characteristics extremely resistant to bending, but such shafts are undesirably too heavy and costly to use.
An object of the present invention is to provide a double transport drum-roller machine in which the use of a roller shaft extremely resistant to bending is unnecessary, and yet provides along the total axial length of the roller uniform relief from it's weight.
The present invention is based on the fact that the surface pressure applied to the web-wrapped drum exerts a much greater influence on the roller tension, which tension determines the tightness of the rolling operation, than the surface pressure applied by the roller on the drum not wrapped by the web-formed material. Therefore, weight relief applied to the roller is made where the influence on the tightness of the rolling is greatest. The surface pressure of the roller against the web-wrapped drum is decreased by counteracting the weight of the roller against the drum by engaging a relief drum on the roller. By appropriately controlling the forces of a load drum and the relief drum against the roller, the surface contact or weight of the roller on the web-wrapped drum can be sensitively and responsively influenced and adjusted in such a manner that the web-formed material is initially wound more tightly on the roller, and as the winding process progresses, the material is wound less tightly about the roller. Further, because the relief drum is engaged peripherally along the axial length of the roller, the double transport drum-roller machine of the present invention can be used with very large roller widths or axial lengths.
In the double transport drum-roller machine of the present invention, the load or weight of the roller is primarily retained or supported by the drum not wound with the web-formed material, thereby to support the roller along its's total axial length to prevent any bending thereof. Moreover, at any point along the axial length of the roller, the tightness of the wind can be uniformly adjusted to the same degree.
In view of the above, the double transport drum-roller machine of the present invention has unlimited application for rollers of any axial length.
Another advantageous feature of the present invention is the provision of rocking levers pivotally connected to the roller machine and which carry the relief drum thereon. The pivot axes of the rocking levers are installed coincident with the axis of the web-wrapped transport drum to provide a compact arrangement. Furthermore, since the relief drum is operative on the roller during the rolling process, a drive mechanism is provided to equalize the peripheral rate of the relief drum with that of the roller.